A hacker who claims he was behind a fast-spreading e-mail worm that crippled corporate networks last week said that the worm was designed, in part, as a propaganda tool.

The hacker, known as Iraq Resistance, responded to inquiries sent to an e-mail address associated with the "Here you have" worm, which during a brief period early Thursday accounted for about 10 percent of the spam on the Internet. He (or she) revealed no details about his identity, but said, "The creation of this is just a tool to reach my voice to people maybe... or maybe other things."

He said he had not expected the worm to spread as broadly as it had, and noted that he could have done much more damage to victims. "I could smash all those infected but I wouldn't," said the hacker. "I hope all people understand that I am not negative person!" In other parts of the message, he was critical of the U.S. war in Iraq.

On Sunday, Iraq Resistance posted a video echoing these sentiments and complaining, through a computer-generated voice, that his actions were not as bad as those of Terry Jones. Jones is the pastor at a small Florida church who received worldwide attention this week for threatening to burn copies of the Koran.

Security experts agree that the worm could have caused more damage. However, it did include some very malicious components, such as password logging software and a backdoor program that could have been used to allow its creator to control infected machines. But because the software was not terribly sophisticated, it was quickly shut down as Web servers that it used to infect machines and issue new commands were taken offline last week.

"Here you have" spread when victims clicked on a Web link and then allowed a malicious script to run on their computer.It is the more-successful follow-up to an August worm that included the e-mail address that Iraq Resistance used to communicate with the IDG News Service.

According to Cisco, the worm accounted for between 6 percent and 14 percent of the world's spam for a few hours Thursday. It primarily gummed up corporate e-mail networks in the U.S.

It is the first worm in years to have such a widespread and noisy effect, hearkening back to the days of the Anna Kournikova worm. Nowadays, most malware writers don't want to draw attention to their activities, because they generally want to keep their malicious software hidden away on victims' computers as long as possible.

Disney, Proctor and Gamble, Wells Fargo and the U.S. National Aeronautics and Space Administration (NASA) are among the organizations reported to have been hit by the worm.

Tariq ibn Ziyad was the eighth century commander who conquered much of Spain on behalf of the Umayyad Caliphate. Iraq Resistance's YouTube video has a Spanish theme too. It shows a map of Andalucia, and Iraq Resistance lists his location as "Spain" in his YouTube profile.

In his e-mails, Iraq Resistance did not answer questions about his identity, saying that he was worried about his safety. "I think this information is enough for you and having more looks like [an] investigation," he said. "I don't see myself that criminal."

Robert McMillan covers computer security and general technology breaking news for The IDG News Service. Follow Robert on Twitter at @bobmcmillan. Robert's e-mail address is robert_mcmillan@idg.com